The present invention relates to a method for determining a target rotational speed below the application rotational speed of a washing drum, as well as a method for treating laundry by using the aforementioned method. The invention further relates to a laundry treatment device which is provided with a control element for carrying out the method according to the invention.
Washing and/or rinsing methods are already known from the prior art for automatic washing machines in which, for improving the washing effect, the washing drum during the washing and rinsing process is driven intermittently at alternating rotational speeds and in alternating rotational directions. Such a method is disclosed in EP 0 618 323 A1. In this method, the laundry is intended to absorb water during the washing or rinsing operation at a rotational speed which is considerably below the so-called application rotational speed, in which the laundry is forced against the drum wall by centrifugal force. As a result of this low rotational speed, it is intended that the laundry is wetted as thoroughly as possible. During operation at a rotational speed which is considerably above the application rotational speed, the absorbed water is intended to be driven out of the laundry again. This method is also known as washing-spinning.
Washing drums are also available which are provided with a scoop device. If such a scoop device is present, the rotational speed and the rotational direction are selected such that the scoop device additionally assists the water absorption of the laundry. Thus, in this known method thorough wetting of the laundry is achieved. This method is disadvantageous, in particular, with large laundry loads. In this case only weak washing mechanics are exerted on the laundry. During operation of the washing drum at rotational speeds which are considerably below the application rotational speed, the laundry executes a so-called rolling motion. The washing mechanics, consisting of compression and friction between the individual laundry items is considerably reduced in the aforementioned method of EP 0 618 323 A1 when operated at rotational speeds considerably below the application rotational speed. When the washing drum is driven above the application rotational speed, the washing mechanics are entirely absent as the individual items of the laundry adhere firmly to the washing drum wall.
Based on the aforementioned method, in the prior art attempts have already been made to increase the washing mechanics by the preselection of set, variable rotational speeds. Improved washing mechanics are desirable, in particular, with non-delicate laundry as otherwise too little cleaning effect is achieved and an optimal washing result may not be achieved.
In DE 103 26 551 A1 it is, therefore, proposed within the washing and/or rinsing process to drive the washing drum in at least one phase of intensive wetting of the laundry and in at least one phase of high washing mechanics. These phases succeed one another at least once within the washing and/or rinsing process. In the phase of intensive wetting of the laundry, the speed of the washing drum is changed in one direction to a rotational speed considerably above the application rotational speed and in the other direction to a second rotational speed considerably below the application rotational speed. In the phase of high washing mechanics, the washing drum is accelerated in both rotational directions to rotational speeds at which the individual laundry items are strongly compacted and are rubbed vigorously against one another. However, a method is not disclosed by which the optimal rotational speeds for the aforementioned phases are determined for one respective washing program, one respective type of laundry and one respective load.
In DE 196 19 603 A1 it is proposed to tackle variable load quantities and the resulting different degrees of mechanical washing effects at a fixed rotational speed, by the rotational speed being alternately increased or reduced, depending on the respective position of the entrainers. In this case, however, as before there is the drawback that the alteration of the rotational speed is not dependent on the different loads.